416E, 420E and 430E Backhoe Loaders Charging System Caterpillar

System Operation Description:

Often when problems with the charging system are being investigated, the alternator is not the problem. If a low battery condition is present test the batteries first. See Special Instruction, SEHS7633, "Battery Test Procedure" for more information. If the engine cranks slowly, then test the starting system. See Service Magazine, SEPD0020, "Testing The Starter On The Engine" for more information. If a warning indicator for the charging system is ON, see Service Magazine, SEBD1751, "Difference Between Alternator Indicator In Electronic Monitoring System (EMS) And Low Voltage Indicator In Operating Monitoring System (OMS)".

Note: Severely discharged batteries can cause low system voltage. Severely discharged batteries can occur even while the engine is running above idle, and the alternator is working properly. Proper low engine idle is also important.

Test Step 1. DETERMINE THE METHOD OF EXCITATION FOR THE ALTERNATOR.

1. Check the rear of your alternator in order to determine the method of excitation. See table 1 in order to verify the proper alternator excitation.

Expected Result:

Test method 1. These alternators have a "1", "REG", or "D+" terminal. Test method 2. These alternators are self-excited. Test method 3. These alternators have a "IG" terminal.

Results:

• Method 1 - The alternator has a "1", "REG", or "D+" terminal. Proceed to test step 2.

• Method 2 - The alternator is self-excited. Proceed to test step 4.

• Method 3 - The alternator has an "IG" terminal. Proceed to test step 3.

Test Step 2. CHECK THE RESISTANCE IN THE EXCITATION CIRCUIT.

1. Turn the key start switch to the ON position.

2. Verify voltage at the excitation terminal. Connect the red lead from a multimeter to the excitation terminal. Connect the black lead to a ground source (alternator case ground).

3. Read the voltage that is shown on the multimeter.

Expected Result:

The voltage reads at least .2 volts.

Results:

• YES - The voltage reads .2 volts or more. The excitation circuit is correct. Proceed to test step 4.

• NO - The voltage is less than .2 volts. There is a problem in the wiring harness to the alternator or there is a poor electrical connection. Correct the problem and operate the machine. Watch for a recurrence of the problem.STOP

Test Step 3. CHECK THE RESISTANCE IN THE EXCITATION CIRCUIT

Note: This step is only for alternators with external excitation when the terminal for excitation is labeled: "IG".

1. Turn the key start switch to the ON position.

2. Verify voltage at the excitation terminal. Connect the red lead from a multimeter to the excitation terminal. Connect the black test lead to a ground source (alternator case ground).

   Note: For G3B, K3A, and L3A alternators, Insert a 7X-1710 Multimeter Probe Group into the rear of the middle wire in the connector. See figure 1 below. Insert the probes spoon lead between the seal and the wire that surrounds the wire and the outer shell of the connector. Do not insert the probe between the wire insulation and the black seal. This terminal (IG) is the terminal for excitation.

Show/hide table



Illustration 1	g00496660
Special technique for alternators: G3B, Y3A and L3A.

3. Read the voltage that is shown on the multimeter.

Expected Result:

The voltage measurement is within .5 volts of the battery voltage.

Results:

• YES - The voltage reads battery voltage. The excitation circuit is correct. Proceed to test step 4.

• NO - The voltage is less than .5 volts of the battery. There is a problem in the wiring harness to the alternator or there is a poor electrical connection. Correct the problem and operate the machine. Watch for a recurrence of the problem.STOP

Test Step 4. CHECK THE SYSTEM VOLTAGE.

1. Before you start the machine, connect a voltmeter between the "B+" terminal and the case of the alternator. Turn OFF all electrical loads.

2. Turn the key to the ON position but do not start the engine. Read the voltage on the voltmeter. Make a note of the voltage that was measured.

Expected Result:

This voltage should be approximately system voltage.

Results:

• YES - The voltage is approximately system voltage. Proceed to test step 5.

• NO - The voltage is less than system voltage. Proceed to test step 7.

Test Step 5. CHECK THE OPERATION OF THE ALTERNATOR.

1. The voltmeter remains connected between the "B+" terminal and the case of the alternator.

2. Start the machine. Set the throttle to at least 75 percent. Read the voltage on the voltmeter. Make a note of the voltage that was measured.

Expected Result:

The voltage measurement is greater than the voltage that was recorded in the previous test step "Check The System Voltage".

Results:

• VOLTAGE HIGHER - The voltage measurement is greater than the voltage that was observed in the previous test step "Check The System Voltage". The voltage is also less than the maximum voltage that is listed in the specifications for the alternator. The alternator is partially charging the battery. Proceed to test step 6.

• VOLTAGE TOO HIGH - The voltage measurement is greater than the voltage that was observed in the previous test step "Check The System Voltage". The voltage is also greater than the maximum voltage that is listed in the specifications for the alternator. The alternator is over charging. Proceed to test step 19.

• VOLTAGE LOWER - The voltage is not higher than the voltage that was observed in the previous test step. Proceed to test step 7.

Test Step 6. TEST THE ALTERNATOR OUTPUT.

Note: For the proper output current, refer to table 1.

1. Ensure that the batteries are NOT fully charged.

   Note: A fully charged battery may have open circuit voltage above 12.5 V on 12 V systems. 24 V systems may be as high as 25 V.

2. If the batteries are fully charged, then crank the engine for 30 seconds. This action reduces the battery voltage. Operate the lights for 10 minutes while the engine is off as an alternative.

3. Connect the 9U-5795 Current Probe to a DMM (digital multimeter) or use a 225-8266 Ammeter Tool Gp . The multimeter must have a peak hold feature. Clamp the probe around the alternator output wire "B+". Before you clamp the probe around the wire, ensure that the probe is "zeroed".

4. Set the digital multimeter to "peak hold" or "max mode" on the "mV" scale.

5. Turn on all electrical accessories: lights, air conditioning and radio.

6. Start the machine, and immediately set the throttle to at least 75 percent. The peak current will appear on the voltmeter in "peak hold" or "max" mode.

Expected Result:

The current reading should be at least 90 percent of the specified peak output.

Results:

• YES - The current is at least 90 percent of the specified peak output. Proceed to test step 13.

• NO - The current is less than 90 percent of the specified peak output. Proceed to test step 7.

Test Step 7. CHECK THE DRIVE SYSTEM OF THE ALTERNATOR.

1. Check the condition of the alternator drive belt. Clean the pulley and replace the drive belt if the drive belt is oily. Dry the drive belt if the belt is wet. Replace the drive belt, if the belt is worn.

2. Check the tension of the alternator drive belt. Adjust the drive belt to the correct tension.

3. Check the nut on the alternator pulley. Tighten the nut if the nut is loose.

Expected Result:

The drive system of the alternator is functioning correctly. No corrections to the drive system were necessary.

Results:

• YES - The drive system of the alternator is functioning correctly. No corrections were necessary. Proceed to test step 8.

• NO - The drive system of the alternator was not functioning correctly. Corrections were necessary.

  Repair: Ensure that the problems have been corrected. Exit this procedure and retest the alternator charging system.

  STOP

Test Step 8. TEST THE CHARGING CIRCUIT.

1. Verify that the nut on the "B+" alternator terminal is tight. Also, verify that the wire has a good connection to the "B+" terminal.

2. Many AVSpare machines are equipped with a connector for the 6V-2150 Starting/Charging Analyzer . Use of this tester replaces the remainder of this test step. To operate the analyzer, refer to Tool Operating Manual, SEHS7768, "Using the 6V-2150".

3. Start the engine and set the throttle to at least 75 percent. Turn ON all electrical accessories for the remainder of this test step. Allow the engine to run for at least 3 minutes before continuing.

4. Measure the voltage between the "B+" alternator terminal and the alternator case ground. Make a note of the measured voltage. Perform the next measurement immediately.

5. Measure the voltage across the battery. Put the red lead on the battery positive terminal, and put the black lead on the battery negative terminal. Make a note of the voltage that was measured.

Expected Result:

The voltage at the battery should be less than the voltage at the alternator. The difference in voltages should not be more than 1 V on 12 V systems. The difference should not be more than 2 V on 24 V systems.

Results:

• YES - The voltage at the battery is less than the voltage at the alternator. Also, the difference in voltages is less than 1 V for 12 V systems and the difference is less than 2 V for 24 V systems. The wiring that is related to the alternator is correct at this time.

  Repair: There is an internal problem with the alternator. Repair the alternator or replace the alternator.

  STOP

• NO - The voltage at the battery is less than the voltage at the alternator. However, the difference in voltages is greater than 1 V for 12 V systems and the difference is greater than 2 V for 24 V systems. Proceed to test step 9.

Test Step 9. TEST THE POSITIVE SIDE OF THE CHARGING CIRCUIT.

1. Measure the voltage between the frame ground and the "B+" alternator terminal. Make a note of the voltage that was measured. Perform the next measurement immediately.

2. Measure the voltage between the frame ground and the + battery post. Make a note of the voltage that was measured.

Expected Result:

The voltage difference does not exceed 1 V on 24 V systems or 0.5 V on 12 V systems.

Results:

• YES - The voltage difference does not exceed the tolerance. The positive circuit is good. Proceed to test step 10.

• NO - The voltage difference exceeds the tolerance.

  Repair: There is high resistance in the positive side of the charging circuit that is caused by one of the following conditions:

  • An electrical connection has loosened.

  • An electrical connection has corroded.

  • The main relay has failed.

  • A circuit breaker has failed.

  Repair the problem or replace any component that has failed. Exit this procedure and retest the alternator charging system.

  STOP

Test Step 10. TEST THE NEGATIVE SIDE OF THE CHARGING CIRCUIT.

1. Check the voltage between the negative battery post and the alternator case ground.

Expected Result:

The voltage does not exceed 1 V on 24 V systems or 0.5 V on 12 V systems.

Results:

• YES - The voltage difference does not exceed the tolerance. The negative circuit is good. Proceed to test step 11.

• NO - The voltage difference exceeds the tolerance.

  Repair: There is high resistance in the negative side of the charging circuit that is caused by one of the following conditions:

  • An electrical connection has loosened.

  • The alternator ground has loosened.

  • The engine ground has opened.

  Repair the problem or replace any component that has failed. Exit this procedure and retest the alternator charging system.

  STOP

Test Step 11. TEST THE CIRCUIT OF THE "R" TERMINAL.

1. Start the engine and set the throttle to at least 75 percent.

2. Connect a voltmeter between the "B+" terminal and the alternator case ground.

3. Disconnect the wire from the "R" terminal. Select "YES" if the "R" terminal is not used on the machine.

Expected Result:

The voltage does not change.

Results:

• YES - The voltage does not change. Proceed to test step 12.

• NO - The voltage rises and the alternator begins charging.

  Repair: The wire to the "R" terminal is shorted. Repair the wiring or replace the wiring. Exit this procedure and retest the alternator charging system.

  STOP

Test Step 12. RESTORE THE RESIDUAL MAGNETISM OF THE ROTOR.

1. Connect one end of a jumper wire to the "B+" terminal ("D+" terminal for K1, N1, and N3) of the alternator.

2. Connect the other end of the jumper wire to the "R" terminal of the alternator for 2 seconds.

Expected Result:

The voltage output rises on the "B+" terminal. The residual magnetism of the rotor has been restored.

Results:

• YES - The voltage output rises. The residual magnetism of the rotor has been restored. The alternator is now charging.

  Repair: Exit this procedure and retest the alternator charging system.

  STOP

• NO - The voltage output does not rise.

  Repair: There is an internal problem with the alternator. Repair the alternator or replace the alternator.

  STOP

Test Step 13. TEST FOR UNDESIRABLE CURRENT FLOW IN THE ALTERNATOR CHARGING SYSTEM.

1. Turn off all of the accessories. Turn the keyswitch to the OFF position.

2. Clamp a 9U-5795 Current Probe or 225-8266 Ammeter Tool Gp around the main ground cable. Clamp the tool with the positive side away from the battery. Reset the probe (zero) before you clamp the probe around the wire. Read the current on the meter. Make a note of the current that was measured.

Expected Result:

The current is below 2 A. The "YES" selection is dependent on the presence of a main disconnect switch on the machine that is being tested.

Results:

• YES - WITH DISCONNECT SWITCH - The current is below 2 A. For machines with a main disconnect switch, proceed to test step 14.

• YES - WITHOUT DISCONNECT SWITCH - The current is below 2 A. For machines without a main disconnect switch, proceed to test step 15.

• NO - The current is above 2 A. There is a current draw in the system. Proceed to test step 16.

Test Step 14. MEASURE THE CURRENT OF THE SYSTEM BY USING THE MAIN DISCONNECT SWITCH.

1. Turn the disconnect switch to the ON position.

2. Connect a multimeter across the disconnect switch terminals. Connect the red lead to the terminal on the frame side. Connect the black lead to the terminal on the battery side. Use the 10A connections in order to avoid damage.

3. Turn the disconnect switch to the OFF position and read the current. Make a note of the measured current.

Note: The standard acceptable current draw is 50 mA. A current draw above 50 mA usually indicates a problem. However, some large machines with multiple electronic control modules have a higher acceptable limit. For more information, contact a AVSpare dealer or contact the business unit that produces the machine.

Expected Result:

The current is below 0.050 A (50 mA).

Results:

• YES - The current is below 0.050 A. The charging system is functioning properly at this time. The failure is possibly an intermittent draw in the system. The batteries may have failed. Ensure that NO accessories were ON during the test. Exit this procedure and retest the alternator charging system.STOP

• NO - The current is above 0.050 A. There is a draw in the system. Proceed to test step 16.

Test Step 15. MEASURE THE CURRENT OF THE SYSTEM BY REMOVING THE NEGATIVE BATTERY CABLE.

1. Disconnect the ground cable from the negative battery post. There may be more than one battery that is connected to ground. Disconnect all of the batteries that are connected to ground. Do not disconnect cables that are between batteries that are connected in series.

2. Connect a multimeter between the disconnected battery ground cable and one of the negative battery terminals. Connect the red positive lead of the multimeter to the cable. The negative lead should be connected to the battery terminal. Use the 10A connections in order to avoid damage.

Note: The standard acceptable current draw is 50 mA. A current draw above 50 mA usually indicates a problem. However, some large machines with multiple electronic control modules have a higher acceptable limit. For more information, contact a AVSpare dealer or contact the business unit that produces the machine.

Expected Result:

The current is below .050 A (50 mA).

Results:

• YES - The current is below 0.050 A. The charging system is currently good. The problem is a possible intermittent current draw in the system. The batteries may have failed. Check that NO accessories were ON during the test.STOP

• NO - The current is above 0.050 A. There is excessive current flow in the system. Proceed to test step 16.

Test Step 16. TEST THE CURRENT OF THE ALTERNATOR OUTPUT BELOW 2 AMPERES.

1. Turn the keyswitch to the OFF position.

2. Connect the 9U-5795 Current Probe to a DMM (digital multimeter) or use a 225-8266 Ammeter Tool Gp . Clamp the probe around the "B+" wire of the alternator. Before you clamp the probe around the wire, ensure that the probe is "zeroed".

3. Read the current on the meter. Make a note of the current that was measured.

Expected Result:

The current is under 2 A.

Results:

• YES - The current is under 2 A. Proceed to test step17.

• NO - The current is over 2 A.

  Repair: There is an internal problem with the alternator. Repair the alternator or Replace the alternator.

  STOP

Test Step 17. TEST THE OUTPUT CURRENT OF THE ALTERNATOR BELOW 0.015 AMPERES.

1. Disconnect the wire from the "B+" terminal of the alternator. Set the multimeter on the 10 amp scale. Connect the red lead of the multimeter to the wire that was disconnected. Connect the black lead of the multimeter to the "B+" terminal of the alternator. Make a note of the current that was measured.

Expected Result:

The current is less than 0.015 A.

Results:

• YES - The current is under 0.015 A. The alternator is operating correctly. There may be a current draw on the machine. Proceed to test step 18.

• NO - The current is over 0.015 A.

  Repair: There is an internal problem with the alternator. Repair the alternator or replace the alternator.

  STOP

Test Step 18. IDENTIFY THE SOURCE OF EXCESSIVE CURRENT DRAW.

1. Make sure that every electrical component is turned OFF. Make sure that the keyswitch is turned OFF. Make sure that the dome lights are OFF.

2. Clamp a 9U-5795 Current Probe or 225-8266 Ammeter Tool Gp around the main ground cable. Clamp the tool with the positive side away from the battery. Reset the probe (zero) before clamping the probe around the wire. Use the current probe if the draw is above approximately 2 A. Use the Ammeter if the draw is below approximately 2 A.

3. Remove the fuses or open the circuit breakers one at a time. Check the current after each fuse has been removed or each circuit breaker has been opened. After observing the current, reinstall the fuse or close the circuit breaker. Start with the main circuits first, and proceed to smaller circuits.

4. Check if any components on the circuit are ON.

5. If everything is OFF, then disconnect electrical components on the circuit one at a time. Monitor the current after each component is disconnected.

6. All of the components in the circuit should be disconnected. If the problem still exists, then check the wiring in the circuit. There may be circuit leakage through corrosion or circuit leakage through a short.

   Note: The standard acceptable current draw is 50 mA. A current draw above 50 mA usually indicates a problem. However, some large machines with multiple electronic control modules have a higher acceptable limit. For more information, contact a AVSpare dealer or contact the business unit that produces the machine.

Expected Result:

The source of the excessive current draw was determined.

Results:

• YES - The source of the excessive current draw was determined.

  Repair: Repair the problem or replace any component that has failed. Exit this procedure and retest the alternator charging system.

  STOP

• NO - The source of the excessive current draw was not determined.

  Repair: Exit this procedure and retest the alternator charging system.

  STOP

Test Step 19. TEST FOR AN OVERCHARGING CONDITION FROM THE ALTERNATOR.

1. Verify that the nut on the "B+" alternator terminal is tight. Also, verify that the wire has a good connection to the "B+" terminal.

2. Many AVSpare machines are equipped with a connector for the 6V-2150 Starting/Charging Analyzer . Use of this tester replaces the remainder of this test step. To operate the analyzer, refer to Tool Operating Manual, SEHS7768, "Using the 6V-2150".

3. Start the engine and set the throttle to at least 75 percent. Turn ON all electrical accessories for the remainder of this test step. Allow the engine to run for at least 3 minutes before continuing.

4. Measure the voltage between the "B+" terminal of the alternator and the case of the alternator. Make a note of the voltage that was measured. Perform the next measurement immediately.

5. Measure the voltage across the battery. Put the red lead on the positive terminal of the battery, and put the black lead on the negative terminal of the battery. Make a note of the voltage that was measured.

Expected Result:

The voltage at the battery should be less than the voltage at the alternator. On systems that are 12 V, the difference in voltages should not be more than 1 V. On systems that are 24 V, the difference should not be more than 2 V.

Results:

• YES - The voltage at the battery is less than the voltage at the alternator. Also, the difference in voltages is less than 1 V for 12 V systems and the difference is less than 2 V for 24 V systems. The wiring that is related to the alternator is correct at this time.

  Repair: There is an internal problem with the alternator. Repair the alternator or Replace the alternator.

  STOP

• NO - The voltage at the battery is less than the voltage at the alternator. However, the difference in voltages is greater than 1 V for 12 V systems and the difference is greater than 2 V for 24 V systems. Proceed to test step 20.

Test Step 20. TEST THE POSITIVE SIDE OF THE CHARGING CIRCUIT.

1. Measure the voltage between the frame of the machine and the "B+" terminal of the alternator. Make a note of the voltage that was measured. Perform the next measurement immediately.

2. Measure the voltage between the frame of the machine and the positive terminal of the battery. Make a note of the voltage that was measured.

Expected Result:

The voltage difference does not exceed 1 V on 24 V systems or 0.5 V on 12 V systems.

Results:

• VOLTAGE OK - ALT. WITHOUT IG/S TERM. - The voltage difference does not exceed the tolerance. The positive circuit is good.

  Repair: There is an internal problem with the alternator. Repair the alternator or Replace the alternator.

  STOP

• VOLTAGE EXCESSIVE - ALL ALT. - The voltage difference exceeds the tolerance.

  Repair: There is high resistance in the positive side of the charging circuit that is caused by one of the following conditions:

  • An electrical connection has loosened.

  • An electrical connection has corroded.

  • The main relay has failed.

  • A circuit breaker has failed.

  Correct the problem. Exit this procedure and retest the alternator charging system.

  STOP

• VOLTAGE OK - ALT. WITH IG/S TERM. - The voltage difference does not exceed the tolerance. The positive circuit is good. Proceed to test step 21.

Test Step 21. TEST FOR OVERCHARGING

1. Start the engine and set the throttle to at least 75 percent.

2. Measure the voltage between the sense terminal (S) and/or the "IG" terminal to the case of the alternator.

Expected Result:

The voltage at the "S" terminal and/or "IG" terminal is above the specification.

Results:

• YES - The measured voltage exceeds the specification. There is an internal malfunction in the alternator. See the appropriate service manual for the alternator in order to test the internal components and connections.STOP

• NO - The voltage from the "B+" terminal to the case of the alternator is below the measurement that was taken in the initial tests. The sense circuit in the generator set has high resistance. Correct the problem. Exit this procedure and retest the alternator charging system.STOP